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Dr. Dan Ahrens

Dr. Dan Ahrens DVMDr. Ahrens had completed his courses for a master’s degree in biochemistry at University of Texas A&M in the area of nutrition when he was accepted into veterinary school. He quit graduate school and immediately enrolled in veterinary college. His interest in nutrition has remained during his career as a veterinarian. This interest and his years of consultations with Dr. Wessels, a DVM with a PhD in physiology/nutrition that lives in upstate New York, concerning specific patient’s nutritional needs has allowed our clinic to keep up with current scientific breakthroughs in nutrition and diets. This is one of the reasons our clinic offers organic fresh frozen foods for pets with no preservatives, sugars, or dyes. If clients choose to use a commercial prepared kibble, Dr. Ahrens stresses the importance of quality meat based diets without harmful chemicals.
While his duties at VMDAH are primarily research and management, he is still keenly interested in the everyday healthcare for your beloved pets. Dr. Ahrens has brought innovative technologies to VMDAH such as in house stem cell treatments, PRP (Platelet Rich Plasma) therapy, and the latest in cold laser supportive therapy. Dr. Ahrens continues his education by working on becoming certified in Homeopathy amongst other modalities. He is a certified canine rehabilitation practitioner by the University of Tennessee College of Veterinary Medicine. He is a member of the American Veterinary Medical Association, Texas Veterinary Medical Association, Harris County Veterinary Medical Association, Montgomery County Veterinary Medical Association, American Holistic Veterinary Medical Association, American Association of Veterinary Acupuncturist, and International Veterinary Association of Pain Management. 

Dr. Lisa Knapp

Dr. Lisa Knapp DVMDr. Knapp is a 1989 Graduate of Texas A&M University. She is certified by the American Veterinary Chiropractic Association and is a certified animal acupuncturist through the International Veterinary Acupuncture Society. She applies all her postdoctoral skills daily in the practice because of her special interest in sports medicine. Dr. Knapp has actively competed in local and national agility trials for the last 17 years. She is the reason an agility team chose to use our agility yard for their practices. Dr. Knapp is a skilled surgeon and shows a keen interest in internal medicine and has been with Veterans Memorial Drive Animal Hospital for 20 years When not hard at work or solving cases, Dr. Knapp spends quality time with her husband, two children (Allen and Amelia), two Shelties (Andy and Sable),two cats (Junior and Tammy),one guinea pig (Pillsbury), an African Grey (Kingpin) and a beta. (The Knapp's are working on the name!) We appreciate her hard work, countless hours, dedication and contributions to Veterans Memorial Drive Animal Hospital. She is very valuable to us, and her clientele will surely agree that Dr. Knapp goes above and beyond the call of duty, and we are very fortunate to have her on our team. She is a member of the American Veterinary Medical Association, Texas Veterinary Medical Association, Harris County Veterinary Medical Association, American Holistic Medical Association, American Association of Veterinary Acupuncturist, and American Veterinary Chiropractic  Association.

Dr. Juan Ayala, Managing Veterinarian

Dr. Juan Ayala DVMDr Ayala joined Veterans Memorial Drive Animal Hospital in August 2011. Dr. Ayala is bilingual which helps in medical information relay to our Spanish speaking clients. Dr Ayala is the doctor who does our stem surgeries. Dr. Ayala is taking advanced continuing education to be able to provide surgeries at VMDAH and is responsible for over seeing that our veterinary medicine standards meet Dr. Ahrens philosophy. He graduated from Louisiana State University in 2010. He is a member of the American Veterinary Medical Association, Texas Veterinary Medical Association, Harris County Veterinary Medical Association, and a MediVet Accredited Adipose Stem Cell Practitioner.

Dr. Mary A. Crist

Dr. Mary Alissa Crist graduated from Texas A&M University College of Veterinary Medicine in 1989.  After graduation, Dr. Crist practiced in Odessa, Texas (her home area) and then moved to Houston, Texas, to become an associate in 1993 at Veterans Memorial Drive Animal Hospital.   Dr. Mary A. Crist was also a clinical assistant professor at Texas A&M College of Veterinary Medicine in College Station, Texas.  Dr.  Mary Alissa Crist is a published author and has spoken at many veterinary conferences.  She has combined her academic career and her veterinary clinical practice to provide the highest quality veterinary care to all her patients.  She provides both Eastern and Western medicine for Veterans Memorial Drive Animal Hospital.   Dr. Crist is certified in veterinary acupuncture with the International Veterinary Acupuncture Society, Chinese herbology, and is an associate member of the American Veterinary Chiropractic Association.  She held a director position for the International Veterinary Academy of Pain Management which supports her passion for animal pain management and rehabilitation something very near and dear to her heart.

Dr. Mary Alissa Crist has a special interest in performance and sports medicine.  She is involved in competitive dog obedience and conformation and is the proud owner of “Rennie” (GCH CH Courtwood Whirly Girl), a two year old Irish setter, who is ranked in the top 10 and treated with holistic veterinary care.  She also competes with “Shimmers” (JMK She Shimmers), her palomino horse, which is also under her holistic health care.

Dr. Crist enjoys spending quality time with her husband (Jeff) and her two step-daughters (Debbie and Leslie) and her two grandchildren (Tiffany and Brian).  She is a member of the American Veterinary Medical Association, Texas Veterinary Medical Association, Harris County Veterinary Medical Association, American Holistic Medical Association, American Association of Veterinary Acupuncture, International Veterinary Acupuncture Society, American Veterinary Chiropractic Association, and the Irish Setter Club of America.

Dr. Howard Corley

He will be sorely missed by all our staff, his clients, family and friends. He passed away in December 2008 from kidney cancer.

Hospital Manager

Tony Miranda

Tony Miranda Practice ManagerTony Miranda, Penn Hip Cert. - Practice Manager. The buck stops here. He is responsible for the day-to-day management and staffing of VMDAH. Although he has only been involved in veterinary medicine for 20 years, he has advanced through every position the clinic has to offer except veterinarian. He has worked with and been around animals since he was a child. He has completed over 100 hours in equine anatomy, physiology, and neurology, from the Vluggen Institute of Equine Osteopathy in 2008. Although not a veterinarian he has also completed advanced courses in veterinary dentistry, critical care, radiology, anesthesiology, and management. He is currently in charge of scheduling, inventory, and administration, stem cell processing,  platelet rich plasma (PRP) preparation, canine physical rehabilitation, and ozone therapies.
In his time away from the clinic, Tony currently concentrates on hoof health through barefoot methods and other modalities available. Tony dedicates time to farrier work and education, equine health, trail riding, horse training and his Bully dogs. His wife, four children, multiple dogs, cats, and horses keep him very busy when he's not at the clinic.

Vet Techs

Maria Noriega, LVT

Maria Noriega, CVDTMaria is a licensed veterinary technician and is working full time at VMDAH. As you can imagine, her schedule is full. She is bilingual and has enough on-the-job training that she can handle anything that goes on in the treatment and surgery area, plus she has completed an advanced course in veterinary dentistry. She loves pets and has dedicated her life to animals by choosing this as a career. She and her husband have adopted strays and now have at least four dogs and a cat. Her value to our clinic can't be measured. 

Alejandra Trevino

Alejandra Trevino

Alejandra started her internship with us in 2011 while finishing her vet tech program. When she was done with the course in 2012 when  we hired her on as a team member. She is currently working on her state board to become a licensed veterinary technician.


Pet Stylist

Vivian Cuddihee

Vivian joined our team in May of 2017. She is very caring and handles your fur babies with lots of love and gentleness. Call to make an appointment with her here at Veterans Memorial Drive Animal Hospital.